A drive device is conventionally well-known that can reduce rattling noise generated when gear members vibrate in a thrust direction and collide with a case because of rotational variation of helical gears disposed in a drive system of a hybrid vehicle and meshed with each other. For example, this corresponds to drive devices of hybrid vehicles of Patent Documents 1 and 2. In these drive devices, the reduction of the rattling noise is achieved by a control device controlling the drive device and the control device changes an operation point of an engine so as to reduce the rattling noise. For example, a control device of Patent Document 1 controls an engine rotation speed to a predetermined value or higher if a condition of occurrence of the rattling noise is detected in the vehicle power transmission device. When the engine is controlled in this way, the engine is prevented from being operated in a region with large torque variation and the rattling noise is reduced.